4.4. Crocetin and Vitamins Solution Preparation and Treatment

Crocetin (Toronto Research Chemicals, North York, ON, Canada) was dissolved in DMSO (AppliChem, Darmstadt, Germany) to a concentration of 90 mM and kept at -20 °C. For experiments, the stock solution was diluted with culture medium to a final concentration of 1, 10, 50, 100, or 200 µM crocetin, also diluting DMSO to a safe range (0.1–0.2%, i.e., < 0.5% (v/v)). Cells were exposed to crocetin for different incubation times including: (i) for 24 h before exposure to TBHP (pre-treatment), (ii) and/or for 4 h with TBHP (co-treatment), (iii) and/or for 12 h after exposure to TBHP (post-treatment). Ascorbic acid (vitamin C) (Sigma–Aldrich, Taufkirchen, Germany) was dissolved in water and then diluted in culture medium to a concentration of 100 µM. DL-α-tocopherol acetate (vitamin E) (Sigma–Aldrich, Taufkirchen, Germany) was diluted in water to a concentration of 10 mM, then diluted in culture medium to a concentration of 100 µM.